Prom 26: London Sinfonietta/Masson, Royal Albert Hall, London

Its real originality lies in its philosophical exploration of musical modes: the tension between the individual and the mass, and the true nature of folk music. By blending a Pablo Neruda poem with folk lyrics from Polynesia to Peru, and by melding the musical motifs of Balkan Gypsies and Central African pygmies, Berio mints a folk music of his own. He wanted to create the effect of an imaginary musical city, where everyone goes about their business as independently functioning parts of the whole.

Neruda's poem was a furious attack on fascism in both Spain and his native Chile; Berio's message is a celebration of the world's musical diversity, but he makes the poem's key line - "Come and see the blood on the streets" - the leitmotif of a darkening picture of violence. If the opening lyric - "Today is mine/ I claimed to a man" - reflect a Sioux woman's sexual boast, succeeding lyrics from Persia and Polynesia reflect an acceptance that sex may also mean death: "Come close to me/ Even though you have a knife/ To wound me with."

Performed by the London Sinfonietta under the baton of Diego Masson, Berio's vast tapestry rolled out with majestic grandeur. First, an exquisitely limpid duet for soprano and piano, then an incursion of other voices, then a rending crash of untuned brass percussion - and the extraordinary journey was under way. Sometimes, the air shook with massive blocked chords, sometimes it shuddered as brass and woodwind "hocketed" - a Central African technique whereby each instrument plays just one note in a dense mosaic of sounds. Moments of sharp musical focus - a duet for tenor and cello, for example - alternated with periods when it was impossible to see a path through the thickets of sound. When the full poem came through, muttered, shouted, then whispered, Berio's great statement was complete. Magnificent.

The Proms can be heard at www.bbc.co.uk/proms